Lofts and subsidence

[mahonia]

Hi Everyone

We are thinking of doing a loft. It is far more complicated than I ever thought it would be. As SE22 is a subsidence risk area do you think the added weight of a loft could cause subsidence?

Best

M

[Jockey1]

Mahonia

It really depends on your foundations and the local subsidence issues in your area. A good check - look at similar houses close to you and see if any of them have had lofts constructed successfully without subsidence or any other structural issues.

The foundations need to be checked to see if they are adequate for the extra load. The building control officer may instruct you to alter your foundations if unsuitable - at extra cost.

[mahonia]

Hi Jockey1

Thanks very much for that. Do you know who would ask for the foundations to be checked? A structural engineer is doing our plans but did not mentioned this. Would it be building control that would ask for the foundations to be checked?

M

[macroban]

A "structural engineer" who doesn't take account of SE22 building settlement might need changing.

[mahonia]

Hi

Thanks for your reply. The structural engineer that we are using comes highly recommended and has done a lot of work in this area. I must admit I am a bit concerned. He is aware that we want the smallest amount of load possible on the building. He did say something about bore holes when we first saw him but he said that building control never take up this offer...

Not sure what to do as he is really good. I am so confused and want to get this right. Do you think that we should instruct another structural engineer to check the plans and do bore holes even if building control are happy with everything? I have never heard of foundation being checked prior to a loft being done and none of the numerous loft conversion companies we have seen have mentioned it either...

Want to make sure we are water tight when it comes to insurance. We do have their permission to do this work already...

M

[macroban]

Mahonia,

Your further explanation suggests your structural engineer is calculating the load bearing design of your existing footings to see if they need to be reinforced, perhaps by under-pinning, to support the extra loading of the new loft. On the face of it, this is nothing to do with "subsidence". Perhaps just asking him/her outright?

MacRoban

[Jockey1]

Probably a good idea to ask your structural engineer. If he has worked on similar properties he may know the suitability of your property for the desired works.

I'm pretty certain building control will want to see your plans and approve/ammend if necessary.